Traditional illumination usually uses fluorescent lamps as the light source, which allows high speed electrons in argon or neon gas to excite mercury by collision to produce ultraviolet light. The ultraviolet, when strikes a phosphor powder coated in the lamps, emits visible fluorescence for illumination. Since light source provided by this kind of illumination varies with AC current, flickering of the light source may directly affect the users' eyesight. Additionally, the mercury element inside the fluorescent lamps may be harmful to the human bodies. Disposing of the fluorescent lamps may also pollute the environment. Furthermore, applications of this type of lightings require electronic ballast or high-frequency inverter. It also has the shortcomings of slow starting, high power consumption and heat emission.
In light of these concerns, Light Emitting diodes (LEDs) are being developed. Compared to the lighting technique that adopts fluorescent lamps, LEDs is advantageous in having a smaller volume, lower heat emission (less heat radiation), lower power consumption (lower voltage, lower startup current), longer rated life (above 100,000 hours), high reaction speed (can be operated at high frequency), environmental friendly (vibration and impact resistant, recyclable and non-polluting). Additionally, it can be flat packaged, which is useful in development of compact and light products. Therefore, LEDs are becoming the main choices of light sources instead of fluorescent lamps. Details related to the LEDs technologies are for example disclosed in TW Utility Model Pat. No. M286898, M285658 and M284176.
TW Utility Model Pat. No. M286898 discloses an LED sheet lighting, which uses a single-module LED sheet or more than one LED sheets combining together to replace the traditional tubular lightings or projection lightings with high power consumption, weak illuminance and reduced illuminance over time.
TW Utility Model Pat. No. M285658 discloses lighting with improved illuminance, in which an optical shade disposed at the opening of a lamp shell is a transparent optical lens. The inner and outer faces of the optical shade are both concave/convex spherical arcs. A receiving hole is provided in the inner face. At the bottom of the receiving hole is a concave/convex spherical arc face. As such, an LED is located in the receiving hole facing towards the opening of the lamp shell for improved illuminance.
TW Utility Model Pat. No. M284176 discloses a “smart” LED lighting. A control unit and a setting switch designed to provide several setting modes are provided on a circuit board. The control unit is used to provide a LED with a current corresponding to the setting mode received and a luminance signal received by a light sensor. Thereby, the luminance of the lighting can be adjusted according to the ambient luminance in cooperation with the setting mode.
However, in the abovementioned techniques, the total light throughput is small due to the above structures being limited to dispose only one or a limited number of LEDs. Additionally, a LED light source is a point light source, which can not be distributed evenly on the light emergence face.
Moreover, TW Utility Model Pat. No. M286898 and M284176 do not provide any heat dissipating mechanism, the life of the LEDs are reduced due to large heat emission. Although TW Utility Model Pat. No. M285658 incorporates a heat dissipating board, but current goes through the heat dissipating board, i.e. the driving circuit closely abuts the heat dissipating system, which may result in heat loss due to concentrated heat source. This causes loss of optical energy and affects the reliability of the lighting. Furthermore, the above patents lack an over-voltage protection design. Accordingly, in a fixed-current mode, voltage cannot be stabilized at an operating range since the LED driving element cannot provide the over-voltage protection design.
In addition, TW Utility Model Pat. No. M286898 and M284176 do not provide a LED structure that can be easily assembled or disassembled. While only a single LED can be provided in TW Utility Model Pat. No. M285658, the whole lighting fixture needs to be decomposed during assembly or disassembly, so the problem regarding assembly and disassembly still exists.
Therefore, there is a need for an improved illumination technique that addresses the aforementioned shortcomings.